Such a press fitting is known for example from DE 101 18 956 C1. Such a press fitting is also known from DE 197 22 935 C1. Sealing integrity in respect of the smooth-ended pipes which are respectively inserted at the end into the fitting is achieved by the sealing ring being elastically deformed by plastic deformation of the end of the press fitting, which is of a bead-like configuration, in order to come to bear over a given part of the periphery of the cross-section, in line form and/or surface form, against the surface regions, surrounding same, of the bead-like end of the fitting and the pipe. To carry the longitudinal forces which occur at a corresponding internal pressure, the portion of the fitting which adjoins the bead and which is either of a cylindrical or a toroidal configuration is plastically deformed together with the pipe.
After the production of a pipe connection by means of fittings and pipes, they are usually subjected to a pressure test. Any leakage in the region of the connection must be detectable when such a pressure test is carried out. In order to ensure that in any case, it is known for either the fitting, that is to say the bead of the fitting or the sealing ring, to be designed in such a way that they are not sealed in the unpressed condition. That can be implemented either by the dimensioning of the sealing ring and/or the bead or by virtue of a suitable surface configuration of the sealing ring.
DE 101 18 956 C1 for example proposes providing the sealing ring or the sealing element with a large number of small projecting knobs so that the surface of the sealing element, in the unpressed condition, bears only partially against the pipe wall inserted into the press fitting. Thus, in the unpressed condition, that arrangement involves permeability of the sealing ring in the axial direction.
A comparable solution has already been previously proposed in DE 197 22 935 C1. There, the sealing element is provided with a plurality of portions which are disposed in the peripheral direction and which are of a cross-section differing from the initial cross-section, in the form of a bulge which extends over the periphery and into the cross-sectional plane and a recess which is towards the inserted pipe and which extends radially into the cross-section of the sealing element, wherein the volume of the bulge, in comparison with the initial cross-section, is at least as great as the volume of the recess, which is missing in relation to the initial cross-section, and, considered in cross-section, prior to pressing, the recess of the sealing element forms a passage opening in the axial direction.
The sealing element in accordance with that solution is comparatively expensive to produce and requires production tolerances to be observed with the highest level of precision.
The solution in accordance with DE 101 18 956 involves the danger that the fine knobs on the outside surface of the sealing element tear away or are damaged when the pipe ends are pushed in.
Therefore the object of the invention is to improve a press fitting or a sealing element of the kind set forth in the opening part of this specification, such that the above-described disadvantages are avoided.
A plurality of solutions are proposed in accordance with the invention for that purpose.